240: '87 240 pinging. Maybe?

[Cheezmo]

'87 245, B230F, LH2.2, leaky AW71.

So lately I've noticed a slight drop in performance and the other when I was on the highway going up a hill, I noticed some pinging, or what I think was pinging, which sounded like *kak-kak-kak-kak-* which seemed to be about the right circumstances where I'd get pinging. I've also noticed a bit of a tapping in there as well... Would a loose valve or the such cause pinging?

I'll note, I do not have A/C. Well, I don't think it should be engaging the clutch though, since I'm pretty sure there's no pressure in the system and I don't get cold air.

It seems to be while under load rather than at higher speeds.
Also, going downhill and tapping the accelerator to about half-way I can sometimes notice a bit of a misfire, but I'm not sure if that's related or even an issue.

>I'll be checking the vacuum lines, but I tend to keep up on those and have replaced most of them.
>I cleaned the flametrap a couple months back.
>Spark plugs are coming out and I'll check those too.
>Might even pull the camshaft cover and do an inspection.

Anything helps!